This invention relates to an on-board solid carbon dioxide or dry ice refrigeration system for railroad cars (railcars) and more particularly to the construction and methods of use of the dry ice bunker and the freight storage compartment when utilizing carbon dioxide as an expendable refrigerant in transporting products by railroad cars but also useful for other substantially sized vehicles such as trucks, trailers, containers and the like being moved over substantial distances or in circumstances where enroute cold temperature protection is essential, and in an arrangement where no mechanical refrigeration device is included, principally using bunker placement, natural phenomena and insulation choice and techniques to maintain the cargo in the refrigerated state, and especially useful to that cargo in the frozen state.